4.6. List Types

These datatypes
are lists of whitespace-separated items.
The type of these items (called the item type) is defined during the
derivation process (which we will see in the next chapter) and list
datatypes can be derived from any simple type. Three predefined
datatypes are lists (xs:NMTOKENS, xs:IDREFS, and xs:ENTITIES). For all
the list datatypes, the items must be separated by one or more
whitespaces.